“Americans' ownership of stock may ... be more a function of their ability to buy it, than of whether its value is soaring,” Gallup senior editor Lydia Saad said in releasing the survey. “The nation's current [7.5 percent] unemployment rate, while improved, is still too high to support broader stock ownership.”

By contrast, in the decade leading up to 2008, unemployment was generally low enough to support stock ownership by 60 percent or more Americans. The current level of 52 percent, down from 53 percent last spring, is the lowest in Gallup tracking going back to 1998.

The still-high rate of unemployment acts as both a financial and psychological barrier, many market analysts say. People without jobs generally don’t have extra money to invest, while many working Americans may be weighed down by feelings of job insecurity.

Investors' current disposition may also reflect the big share-price declines that Americans observed during the recession – a bad memory that is not erased by several years of share-price recovery.

Another factor, for some investors now, is doubt about how real the economy's recovery is and how long it will last.

One telling indicator: Americans’ attitude about the economy and their own personal finances hasn’t improved much since the deep recession officially ended in mid-2009.

In a new Christian Science Monitor/TIPP poll, for instance, people’s six-month outlook for the economy is more negative than positive, and their personal financial outlook is no more positive than it was in 2009.

The new Gallup survey, which was conducted in early April, asked, “Do you, personally, or jointly with a spouse, have any money invested in the stock market right now – either in an individual stock, a stock mutual fund, or in a self-directed 401(k) or IRA?”

Here are some nuggets from the survey:

• Stock ownership peaked at 65 percent of Americans in 2007, according to the poll results. Interestingly, stock ownership was a bit lower (62 percent) in 2000 as the “dot-com” investing frenzy was peaking.

• Stock ownership has declined among both employed and unemployed Americans and across all income groups. In percentage terms, the biggest decline is a 16 percentage-point drop among middle-income Americans since 2008. Back then, 66 percent of US adults earning between $30,000 and $74,999 owned stock. Today that figure is 50 percent.

• By age, ownership has declined most among people who are between 30 and 64 years old. For that group, 7 in 10 owned stock in 2008, and only about 6 in 10 do now. Stock ownership is lower among younger Americans, but hasn’t declined as much.